An Anne Arundel County man who was found guilty of a burglary based in part on DNA evidence asked a state appellate court Thursday to throw out his conviction, arguing that police improperly kept his genetic information in the database they used to link him to a Coke can from the crime scene.

George Varriale, 46, gave a DNA sample to Anne Arundel County police in 2012 as they were investigating a reported rape. The sample did not link him to that crime, but police later used it to place him at the 2008 burglary of a Glen Burnie business.

Because Varriale was not charged in the rape case, his lawyer told the Court of Special Appeals, police should not have retained his information.

Varriale's appeal challenges the little-known but widely used police practice of holding on to genetic information volunteered by individuals in one case so that it may be used in future investigations.

Critics have called for such records to be thrown out, much like the highly regulated samples that the U.S. Supreme Court has ruled Maryland may take from suspects charged with serious crimes.

Because Varriale volunteered his sample, he was not subject to the same protections — a distinction his lawyer says led to the violation of his rights.

"He did not consent to the state doing what it wants with his DNA for the rest of his life," said defense attorney Thomas Mack.

The case represents the latest front in the battle over police use of DNA in Maryland and beyond. The nation's high court gave its blessing last year to the state law that allows authorities to collect samples from suspects who are charged with serious crimes — but that statute requires police to discard the information when a defendant is cleared.

Police say DNA is an important tool to build strong cases against rapists and other dangerous criminals. But defense attorneys and civil rights groups are concerned that as the databases grow in size and sophistication, they will be used to intrude on the privacy of citizens who have committed no crime.

In another case this week, the state's highest court heard arguments over DNA that was collected without a suspect's knowledge by swabbing the arms of a chair in a police interview room. That case turns on whether people's genetic information, when shed involuntarily, is private.

Varriale's case touches on similar issues. Mack, his lawyer, said in court that Varriale was in the dark about how his information would be used. Mack said investigators went beyond what his client agreed to.

A lawyer for the state countered that police routinely keep material from investigations, such as mug shots and fingerprints, and called the practice innocuous.

The state law that reached the Supreme Court includes protections that do not apply to individuals who volunteer their information. Varriale is among almost 8,000 criminal suspects whose data is on file at Maryland police departments, whether or not they have been convicted of a crime.

The investigation into Varriale began in July 2012, when Anne Arundel County police identified him as a possible suspect in a reported rape.

Varriale, who was living at the time in a small camp behind a liquor store, agreed to let police take swab samples of his DNA and collect his saliva. The samples did not match DNA found on the alleged victim.

But the Police Department uploaded Varriale's information into its DNA database and it came back as a match to the Glen Burnie burglary. He was charged last year, entered a guilty plea that allowed him to appeal, and was sentenced to probation.

The arguments in Varriale's case Thursday centered on the form he signed when he agreed to be swabbed. Mack said that even the detective investigating the rape did not appear to know the genetic data would be kept.

"If you exceed the scope of the consent given, the consent becomes invalid," Mack argued.

But Assistant Attorney General Robert Taylor Jr. said the form gave Varriale fair warning because it included wording that said the DNA could be used "in any future criminal prosecution."

The panel of three judges gave no indication of which way they would rule, but Judge Kevin F. Arthur said the form looked as if it had been written by "someone who failed out of high school English."

Mack said he thought police had intentionally written a misleading form because they did not want to reveal the full scope of what they can do with DNA data.

Maryland authorities have long had the power to collect DNA from felony suspects. A 2008 law empowered police to collect samples from people without their consent if they are charged with violent crimes or serious burglaries.

When legislators expanded the state's DNA law to include collecting information from arrestees, they sought to address concerns over privacy and racial profiling by requiring police to expunge the information of defendants who are not convicted.

With that safeguard in place, Mack argued, if Varriale been arrested in the rape case he likely would not have been charged in the burglary. He wrote in court papers that the lack of protections could deter people from cooperating with police.

The Baltimore Sun reported last year on uses of local DNA databases that critics say are not in the spirit of the state law and allow police to keep the information of innocent people on file.

Police say the law covers only material collected from people who are charged or convicted. Del. Jill P. Carter, a Baltimore Democrat, filed legislation this year to extend the protections.

"We're really allowing DNA from crime victims and completely innocent persons to be stored in … a more liberal way than … we're allowing for arrestee DNA and convictee DNA," Carter said.

A state police official told a legislative committee last month that Maryland's crime labs had signed an agreement not to keep material gathered from living victims. They also pledged not to reuse genetic information volunteered by a suspect in one case in subsequent investigations.

Daniel Katz, the head of the state police crime lab, said the agreement should dispel concerns about lab practices. Katz said Carter's bill would have diminished the ability of officers to solve crimes.

The legislation did not pass, and Taylor wrote in court papers that the General Assembly's lack of action should be taken as a sign that it supports keeping samples collected from suspects.

"The fact is that [keeping the information is] prohibited by neither the Constitution nor Maryland law," he wrote.